Some embodiments relate to a three-phase power converter for converting power between a battery and three-phase time-periodical power grid voltage signals, and a power converter system including the power converter or the three-phase power converter.
Recent drive to abate emissions of automotive vehicles has increased the use of electrical vehicles which are driven by electric motors. Electric motors are supplied by batteries which are periodically charged from a charging station or electrical outlet.
Power converters may provide high power to the battery for charging the battery in reasonable short times. Power converters may thus be used to charge the batteries of passenger vehicles or heavy duty commercial vehicles, such as vans, trucks, buses or the like. Power converters may deliver to the battery a power from a few kilowatts to several hundreds of kilowatts depending on the battery capacity and desired charge times.
Existing power converters for charging batteries typically include a chain of transformers and converters whose one end is connected to a voltage source providing a power grid time-periodical voltage and another end is connected to the battery for delivering the desired power to the battery.
One example of such an existing battery charger is described in Whitaker B, et al., “A High-Density, High-Efficiency, Isolated On-Board Vehicle Battery Charger Utilizing Silicon Carbide Power Devices”, On IEEE Transactions on Power Electronics, VOL. 29, NO. 5, May 2004. Whitaker et al. describes a battery charger consisting of a bridgeless Boost AC-DC Converter and a phase shifted Full-Bridge Isolated DC-DC converter. The bridgeless Boost AC-DC converter converts a power outlet voltage to a direct current voltage (DC) voltage. The phase shifted Full-Bridge Isolated DC-DC converter of Whitaker et al. includes a second converter, implemented by switches for converting the DC voltage again to a time-periodical high-frequency voltage such that a second subsequent transformer can be used for further improving the isolation between the battery and the grid network. The phase shifted Full-Bridge Isolated DC-DC converter of Whitaker et al. further includes a second rectifier, implemented by diodes and a coil, for filtering the high frequency output of the second transformer and providing the desired constant output power for charging the battery.
The first transformer is typically shared between several devices, for example battery chargers as well as household appliances (televisions, refrigerators, personal computers, radios, and the like) wherein each device may require separate isolation. In the existing battery charger the separate isolation can be provided by the second transformer.